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Statement on the recommended
use of pneumococcal 23-valent
polysaccharide vaccine in homeless
persons and injection drug users

Preamble

The National Advisory Committee on Immunization (NACI)
provides the Public Health Agency of Canada with ongoing
and timely medical, scientific and public health advice relating
to immunization. The Public Health Agency of Canada
acknowledges that the advice and recommendations set out in
this statement are based upon the best current available scientific
knowledge and is disseminating this document for information
purposes. People administering the vaccine should also be
aware of the contents of the relevant product monograph(s).
Recommendations for use and other information set out herein
may differ from that set out in the product monograph(s) of the
Canadian manufacturer(s) of the vaccine(s). Manufacturer(s)
have sought approval of the vaccine(s) and provided evidence as
to its safety and efficacy only when it is used in accordance with
the product monographs. NACI members and liaison members
conduct themselves within the context of the Public Health
Agency of Canada’s Policy on Conflict of Interest, including
yearly declaration of potential conflict of interest.

Introduction

As a result of outbreaks of invasive pneumococcal disease (IPD)
among non-elderly adults with a history of homelessness and/or illicit drug use in urban centres in western Canada during
2006-2007, the National Advisory Committee on Immunization
(NACI) reviewed the options for expanding the risk groups for
which 23-valent pneumococcal polysaccharide vaccine (PPV-
23) is recommended. The recommendations in this statement
deal specifically with these groups and present the available data
on their risk of IPD. As well, there is a brief discussion of the
delivery of vaccine programs to these populations.

For the purposes of this statement, homeless persons are
defined as those individuals living in insecure housing either
transiently or chronically. In the literature, there are a number
of terms used to describe individuals who use drugs, for
example “injection drug users”, “intravenous drug users”
or “illicit drug users”. Each study defines which substances
are included and the definition used; data are presented as
described in the primary studies. For these recommendations,
“illicit drug use” refers to both crack cocaine use and
injection drug use.

Prior NACI recommendations

Current recommendations are that PPV-23 should be given
to all persons > 65 years of age and individuals ≥ 5 years of
age at high risk of IPD; children between the ages of 2 and 5
at high risk of IPD should receive conjugate pneumococcal
vaccine followed by PPV-23 in order to increase the
serotype coverage; PPV-23 should be given to high-risk
individuals with co-morbid conditions, such as sickle cell
disease and other sickle cell hemoglobinopathies, other
types of functional or anatomic asplenia, HIV infection,
immunocompromising conditions, pulmonary disease,
diabetes, liver cirrhosis, chronic renal disease, cerebrospinal
fluid leaks or cochlear implants; individuals with risk factors
such as alcoholism and smoking should also receive PPV-
23. For more detailed information related to the use of
pneumococcal vaccines, dosing and contraindications, readers
are referred to the Canadian Immunization Guide(1).

Literature review

A literature review was conducted using the Medline database
from 1 January, 1966, to 1 February 2008. All articles
available in English, of any study design, were retrieved
using the following MeSH subject headings: Streptococcus
pneumoniae, pneumococcal infections, pneumococcal
vaccines, risk factors, substance abuse, intravenous or
homeless persons. The results are presented below.

Homeless populations

Homeless populations have high rates of a variety of respiratory
infections, including S. pneumoniae(2-4). In a 2000-2002
study of adults ≥ 17 years of age presenting to six hospitals and one emergency department in Edmonton, the attack rate
for bacteremic pneumococcal pneumonia was 266.7 per
100,000 person-years among homeless persons, compared
with 9.7 per 100,000 person-years overall. However,
homelessness was not predictive of bacteremic pneumococcal
pneumonia after adjustment for other factors, including
smoking status(5). A recent study using population-based
adult surveillance data in Toronto found that IPD, defi ned
as isolation of the organism from a sterile site, was more
common among homeless individuals, at a rate of 273 per
100,000 per year, than their housed counterparts (9.0 per
100,000 per year)(6).

Overcrowded shelters and pneumococcal carriage rates
among shelter residents as high as 60% can facilitate disease
transmission and outbreaks(7,8). Four clusters or outbreaks of
pneumococcal disease occurring in homeless shelters have
been described in the literature (Table 1). Risk factors in
these pneumococcal outbreaks included alcoholism and age
< 65 years(8,10). Lifetime rates of alcoholism among homeless
persons are estimated at about 60%, and alcohol problems
are approximately 6 to 7 times higher than in the general
population. Homeless persons also suffer disproportionately
from other chronic conditions against which vaccination
with PPV-23 is recommended, such as chronic obstructive
pulmonary disease(2).

Illicit drug use

It is difficult to delineate the risk of pneumococcal disease
associated specifically with the use of illicit drugs, as these
individuals often have other co-morbid conditions such as
HIV infection. As well, the type of drug use varies. The
increased risk of bacterial pneumonia and IPD among HIV-infected
individuals, whether or not they use illicit drugs,
is well-established(11-18), and persons with HIV infection
are already a target group recommended by NACI for
pneumococcal vaccine(1). Few studies have assessed the
risk of IPD among persons who use illicit drugs without
HIV infection (Table 2). In two studies, the incidence of
pneumococcal pneumonia ranged from 1.2 to 3.4 per 1,000
person-years among HIV-negative persons who use illicit
drugs, which was slightly higher than reported rates in the
general population (0.5 to 1.0 per 1,000 person-years) but
much lower than among HIV-positive persons who use
illicit drugs (19 to 35 per 1,000 person-years)(11,14). Among
persons who use drugs and were attending a health service
in Amsterdam, there was no increased risk of self-reported
pneumonia among HIV-negative persons who injected drugs
during the follow-up period as compared with those who did
not inject drugs(13).

Data from the surveillance of IPD in the United States
(U.S.) show that injection drug use does not appear to
additionally predispose these individuals to serotypes that
are more commonly found in adults with HIV (6A, 6B,
9N, 9V, 18C, 19A, 19F and 23F)(19), antibiotic-resistant
forms of pneumococci(19) or death from IPD(20). One study
demonstrated that injection drug users had twice the risk of recurrent IPD than non-users after adjustment for HIV
status and other underlying conditions(20). Persons who use
injection drugs also represented approximately one-quarter of
recurrent episodes of IPD in US Active Bacterial Core (ABC)
Surveillance in 1998, but the potential correlation of a history
of injection drug use with other underlying conditions that
may be associated with recurrent disease was not assessed(21).

Surveillance data show that there is signifi cant overlap
between persons who use illicit drugs and the target groups
recommended to receive pneumococcal vaccine. In a 2001-2003 study of adult IPD patients from six ABC Surveillance
sites, 95% of 38 current injection drug users and 89% of 105
former injection drug users had a pneumococcal vaccine
indication recommended by the US Advisory Committee on
Immunization Practices (ACIP)(22). Multi-centre enhanced
surveillance of 3,031 injection drug users in Canadian
cities showed that 95% reported smoking in the previous
6 months, 13% were HIV-positive, and 40% reported unstable
housing(23).

Table 1. Clusters or outbreaks of pneumococcal disease associated with residing in a homeless shelter

Location

Time period

# Cases
(# deaths)

Predominant serotype(s) (%)

Risk factors and history of vaccination (if reported)

Carriage in shelter population
(n)

Public health measures

Reference Number

US (Chicago)

1968-69

23

5 (20%)
12

Approximately half the cases came from a “skid row” population

9

US (Boston)

January to May 1978

40 (6)

1 (45%)
8 (20%)

61% of type 1 and 18% of non-type 1
cases were associated with immediate
contact with a men’s shelter (p < 0.05)

94% of type 1 cases and 82% of nontype
1 cases were associated with
alcoholism (NS)

Excess of cases in 1978 compared
with 1977 was primarily due to type 1
disease

Delivering immunization programs to homeless
persons and/or those who use illicit drugs

As many homeless persons and persons who use illicit drugs
may not have a regular source of health care, alternative
strategies for reaching these populations may be necessary.
For example, mass immunization campaigns have been
conducted in Vancouver’s Downtown Eastside (DTES),
which has a population characterized by poverty, crowded
housing, homelessness, poor nutrition and hygiene, and
chronic illness. There are an estimated 12,000 injection drug
users residing in the DTES. Pneumococcal immunization
campaigns were conducted in November 1999 (7,575 doses),
November 2000 (1,086 doses) and June 2002 (1,205 doses);
influenza, hepatitis A and hepatitis B vaccines were also
offered during some or all of these campaigns. Sites visited
included single room occupancy hotels, soup kitchens
and food banks, community agencies, fixed-site needle
exchanges, drop-in centres, pubs, medical clinics, parks,
streets and alleys. Vaccine was provided to persons who were
eligible according to NACI recommendations. Few adverse
events were officially reported despite the fact that some
recipients had likely received a previous dose(24,25). Adverse
events related to multiple pneumococcal vaccines have not
been studied adequately to determine the risk it may pose to
individuals. Compared with the year preceding the November
1999 campaign, during the year after it there was a significant
decrease in the number of emergency department visits for
pneumonia (863 and 646 visits respectively; p < 0.001).
Rates of hospital admission for pneumonia through the local
emergency department also decreased, by 25%(26).

Outbreak of S. pneumoniae serotype 5 in urban
centres in western Canada, 2006-2007

From 2005 to 2007, outbreaks of IPD caused by S. pneumoniae
serotype 5 (ST5) occurred in western Canada,
particularly Alberta and British Columbia (B.C.). Two
outbreaks occurring in Vancouver and Calgary are presented
in further detail here.

Alberta

From 2000 to 2004, between 0 and three cases of ST5 IPD
were reported annually to Alberta Health and Wellness,
accounting for < 1% of reported cases of IPD in the province.
In 2005, with earliest reported onset dates in February, the
number of ST5 IPD cases in Alberta increased to 40 (10%
of 383 cases of IPD, all serotypes). The increase continued
dramatically throughout 2006, when there were 204 cases
of ST5 IPD (38% of 539 total cases of IPD). In 2007 there were an additional 220 cases (37% of 597 total IPD cases)
reported. Cases have been reported in all nine regional
health authorities, most occurring in Calgary and Edmonton
(K. Simmonds, Alberta Health and Wellness, 12 March, 2008,
personal communication).

Analysis of IPD cases compiled by the Calgary Area S. pneumoniae Epidemiology Research (CASPER) surveillance
system in 2006-2007 found that ST5 IPD cases had clinical
presentations and multiple risk factors that differed from
those of other IPD (non-ST5) cases that occurred in persons ≥ 16 years. Compared with non-ST5 IPD cases, they were
more likely to have empyema (20% vs 9%, odds ratio [OR]
2.5, 95% confi dence intervals [CI] 1.4 to 4.6) and to have a
chest tube inserted (19% vs 9%, OR 2.5, 95% CI 1.3 to .8);
there was also a trend towards lower mortality (2% vs 9%,
OR 0.3, 95% CI 0.06 to 1.13). Multivariate analysis found
that ST5 IPD cases were significantly more likely to be aged
16 to 64 years (98% vs 66%, OR 9.5, 95% CI 2.2 to 41.4),
homeless (63% vs 12%, OR 3.5, 95% CI 1.8 to 6.6) and users
of illegal drugs (57% vs 11%, OR 6.5, 95% CI 3.6 to 12.0)(27) .
In August 2006, the Alberta PPV-23 high-risk immunization
program was expanded province-wide to include homeless/
disadvantaged individuals. The immunization program was
also expanded to explicitly include those with hepatitis
C virus infection, which was previously included under
chronic liver disease. Regional health authorities have
since been immunizing these groups. In addition, a targeted
immunization campaign in Calgary homeless shelters took
place from 19 to 22 December, 2006, to increase uptake in
this population.

Vancouver, British Columbia

Invasive disease due to ST5 was also previously uncommon
in B.C. (one case per year in 2004 and 2005). In August 2006,
an increase in IPD cases was detected at St. Paul’s Hospital,
which serves Vancouver’s DTES. Forty-six cases of IPD were
admitted in November, compared with the usual monthly
admissions of 0 to 10 cases. Hospital admissions peaked in
December 2006. Between 1 August, 2006, and 12 March,
2007, there were 163 cases of ST5 reported to the BC Centre
for Disease Control, including 125 cases from Vancouver
and 27 cases from Fraser Health Authority, and at least three
deaths. Most cases (78%) reported living in or being exposed
to Vancouver’s DTES (J. Dhaliwal, BC Centre for Disease
Control, 23 March, 2007, personal communication). Of
the cases of serotype 5, 25.6% were homeless individuals.
Frequenting or living in the DTES was also used as an
indication of unstable housing. In univariate analysis,
exposure to DTES was statistically signifi cant (OR 10.25,
95% CI 4.07-25.8, p < 0.001), but once other factors were
controlled for it was no longer significant (OR 7.79, 95% CI
0.91-66.8, p = 0.06). Multivariate analysis identified only
crack cocaine use as a risk factor (OR 12.4, 95% CI 2.22-
69.5, p < 0.01) (R. Gustafson, 1 February, 2008, personal
communication).

In response to the outbreak, pneumococcal immunization
campaigns were launched targeting indigent persons and those
who use illicit drugs in affected urban areas. In November and
December 2006, teams of outreach nurses from Vancouver
Coastal Health conducted PPV-23 immunization of more than
4,000 people in the inner city by targeting shelters, food banks
and other community locations. Immunization of indigent persons and persons who use illicit drugs in regions adjacent to
Vancouver has also been accelerated.

US Active Bacterial Core (ABC) Surveillance of
IPD cases among adults 18 to 64 years in six
reporting sitesn = 2,346

1998-1999

Injection drug users were not significantly more likely to be
infected with “immune-dependent serotypes”* after adjustment
for having HIV/AIDS or other immunocompromising
conditions and being of black race (adjusted OR = 1.05, 95%
CI: 0.77 to 1.44, p = 0.75)

Injection drug users were not significantly more likely to be
infected with “immune-dependent serotypes” after adjustment
for having HIV/AIDS or other immunocompromising
conditions and being of black race (adjusted OR = 1.05, 95%
CI: 0.77 to 1.44, p = 0.75)

Recommendations

In summary, there is evidence from cohort studies, cross-sectional
surveys, outbreak investigations and case reports
that homeless persons have a higher incidence of IPD than
the general population. Also, a high proportion of these
individuals have co-morbidities or risk factors that would
make them eligible for pneumococcal immunization.
Homeless persons living in shelters may be at additional
risk of outbreaks of pneumococcal disease because of the
crowded living conditions and high carriage rates. For
endemic disease, there are methodological difficulties in
determining whether homelessness is causally linked to IPD.
It is recognized that homelessness may be a confounder,
that is, it refl ects the presence of other risk factors that are
disproportionately present in homeless individuals and
contribute to IPD rather than being an independent risk factor.
From the Calgary and Vancouver outbreak data presented
above, there is evidence that homelessness is an independent
risk factor for serotype 5 IPD. There is limited evidence
that persons who use illicit drugs are at increased risk of
pneumococcal disease. The increased risk may be due to the
strong correlation of crack cocaine drug use with underlying
conditions such as smoking and HIV infection.

NACI therefore recommends the following:

The 23-valent pneumococcal polysaccharide vaccine
should be provided to persons who are homeless.

Individuals who use illicit drugs should also be
considered for vaccination with 23-valent polysaccharide
pneumococcal vaccine.

Considerations for future research:

Creative solutions need to be developed to delivering
pneumococcal vaccine to eligible individuals at homeless
shelters, needle exchange programs and/or other sites
where there are homeless populations and people who use
illicit drugs in order to improve vaccine coverage rates in
these populations.

Further research should be done in these populations to
address programmatic issues such as the following:

evaluation of vaccine programs for homeless persons
and illicit drug users in Vancouver, Calgary and
Toronto

tracking of immunization status among those with
varied contact with health care providers, which may
include the use of immunization registries

further determination of the risk of adverse events if
multiple doses of vaccine are given understanding the dynamics of homelessness in
Canada as it relates to the delivery of effective and
efficient immunization services to at-risk individuals

Public Health Agency of Canada. I-Track: enhanced
surveillance of risk behaviours among people who
inject drugs: Phase I report, August 2006. Ottawa:
Surveillance and Risk Assessment Division, Centre for
Infectious Disease Prevention and Control, Public Health
Agency of Canada, 2006.